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Chapter 4

PSYA01H3 Chapter Notes - Chapter 4: Heavy Metal Music, Detection Theory, Gustav Fechner

Course Code
Steve Joordens

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Module 4.1: Sensation and Perception at a Glance
18 year olds attempted to shoot themselves because of “subliminal messages” found in heavy
metal music backwards song contained the phrase “do it”
Sensing the World Around Us
Body has developed an amazing array of specialized processes for sensing and perceiving the
world around us
Sensation the process of detecting external events by sense organs and turning those stimuli
into neural signals
o Sound of someone’s voice is simply noise
Raw sensory information is relayed to the brain
Perception involves attending to, organizing, and interpreting stimuli that we sense
o Recognizes sounds as a human voice
Raw sensations detected by sensory organs are turned into information brain can process through
transduction specialized receptors transform the physical energy of the outside world into
neural impulses
All of our senses use the same mechanism for transmitting information in the brain: action
o Brain is continually bombarded by waves of neural impulses
Doctrine of specific nerve energies differenct senses are separated in the brain
We allocate progressively less attention to stimuli that remain the same over time
Sensory adaptation reduction of activity in sensory receptors with repeated exposure to a
o Allows us to shift focus to important events
Stimulus Thresholds
Willian Gustav Fechner psychophysics: the field of study that explores how physical energy
such as light/sound/intensity relate to psychological experience
Absolute threshold minimum amount of energy or quantity of a stimulus required for it to be
reliably detected at least 50% of the time it is presented
Difference threshold smallest difference between stimuli that can be detected at least 50% of
the time
Signal Detection
Signal detection theory whether a stimulus is perceived depends on both sensory experience
and judgement made by the subject
o Sensory process experimenter presents a faint stimulus or no stimulus at all
o Decision process subject is asked to report whether or not stimulus was actually
Four possible outcomes
o A hit
o Correct rejection
o False alarm
o A miss
Perceiving the World Around Us
Gestalt Principles of Perception
The whole is greater than the sum of its parts
Individual parts of an image have little meaning on their own, but when combined, the whole
takes on a significant perceived form
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Figure-ground principle objects or figures in our environment tend to stand out against a
Proximity and similarity
o We tend to treat 2+ objects that are in close proximity to each other as a group
o We tend to group together individuals that look the same
Continuity perceptual rule that lines or other objects tend to be continuous
Closure tendency to fill gaps to complete a whole object
Backward Messages in Music
Humans are experts at pattern recognition
People have reported finding messages in music when they are played backwards
o Messages could be perceived when music was played forward and influence people’s
Top-down processing when our perceptions are influenced by our expectations or by prior
Bottom-up processing when we perceive individual bits of sensory information and use them
to construct a more complex perception
Attention and Perception
What we pay attention to can affect what we perceive
Often, we are paying attention to more than one stimulus or task at the same time divided
Selective attention focusing on one particular event or task
Top-down task participants selectively attended to single set of events
Inattentional blindness failure to notice clearly visible events or objects because attention is
directed elsewhere
Module 4.2: The Visual System
The Human Eye
Senses information, transfers information to neural impulses, and transfers to brain for complex,
perceptual processing
How the Eye Gathers Light
Primary function of eye gather light and change into an action potential
Where sensation to perception occurs
When light reaches the back of the eye, it stimulates a layer of specialized receptors that convert
light into a message that the brain can interpret transduction
Visual Perception and the Brain
Information from optic nerve travels to numerous areas of the brain
Optic chiasm point at which optic nerves cross at midline of brain
Left half of vision is processed by right hemisphere and vice versa
Lateral geniculate nucleus (thalamus) specialized for processing visual information
o Send messages to visual cortex on occipital lobe
Feature detection cells cells respond selectively to simple and specific aspects of a stimulus
The Ventral Stream “what pathway
Extends from visual cortex on occipital lobe to anterior portions of temporal lobe
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